1. Field of the Invention
This invention generally relates to portable device alert mechanisms and, more particularly, to a linear reciprocal system and method for vibrating a portable device.
2. Description of the Related Art
Typically, vibrations are produced in a portable device to alert the device user of a predetermined condition. For example, in a wireless communications device, the device may be vibrated to alert the user of an incoming telephone call. Vibratory alerts can be used in situations in which an audible alert, such as a ringer, is undesirable or inappropriate. For example, at a concert or a quiet social gathering, an audible ringer would be an unwelcome disturbance.
Conventionally, vibrations in portable devices are produced by an electric motor mounted to the device housing on rubber pads (or other materials having sound dampening qualities). An off-set pendulum weight is attached to the motor shaft, and as the shaft rotates, it sets up an imbalance on the shaft, causing the motor to vibrate. The vibrations of the motor are transferred to the housing via the mounting pads.
There are several disadvantages associated with the conventional vibrating system described above. A wireless communications device is used as an example to illustrate these disadvantages. However, it should be appreciated that these disadvantages apply to other portable devices as well. Advances in technology and manufacturing techniques are resulting in increasingly smaller wireless communications devices, which in turn, have created increasing demands to reduce the size of components used in the devices and to vary the configuration of these components to more efficiently use the space available inside the portable devices. Unfortunately, the motors used in the conventional systems are relatively large and the basic shape of the motors cannot be altered to any great degree. Therefore, the size and inflexibility in the configurability of the motors in the conventional system are obstacles to reducing the size of wireless devices, or may result in the loss of space inside wireless devices for other components.
The trend toward smaller wireless devices along with increases in wireless device functions results in an increase in battery power requirements exacerbated by efforts to reduce battery size. Therefore, minimizing energy consumption in the wireless device is extremely important. Unfortunately, the conventional system includes additional energy consumption in the form of motor bearing losses. Finally, the conventional system creates undesirable audible noise caused by the vibration of the motor and the interaction of the motor and the wireless device housing. Although intended as a silent alarm, vibrators are seldom completely silent.
It would be advantageous if a portable device could be vibrated by a system that was small in size, could be flexibly configured, minimized energy consumption, and did not produce audible noise.